The objectives of this research are to further analyze the role of calcium in muscle regulation in relation to contractile performance. Goals in this approach are as follows: 1) We hope to obtain a better understanding of the various parameters affecting the calcium binding properties of cardiac myosin, particularly the role of the light chains, by studying their immunological characteristics, properties for dissociation and reassociation with the heavy chains, calcium binding properties in the dissociated and reassociated state, and parameters affecting their affinity and number of sites for calcium. Furthermore, we are interested in assessing differences in these properties for various possible isotrophied tissue; 2) In these studies we will develop new mathematical treatment and computer programs for the assessment of the data (i.e., to assess independent sites, sites with interaction, degree of binding, number of binding sites, and binding affinity constants); and 3) Information will be sought to better understand calcium binding in regulation of contraction by assessing competition and binding interaction of various divalent cations.